The present invention relates to an apparatus for cultivating plants and, more particularly, to an apparatus for plant culture which supplies plants with optical energy optimum for their growth by combining collected solar radiation and artificial radiation, which corresponds to skylight.
As well known, the primary requisite for the effective growth of plants is the adequate supply of nourishment, light, carbon dioxide (CO.sub.2), water, etc., as well as optimumly conditioned temperature and humidity. Difficulty has been experienced in satisfying all of such conditions. Another important factor for the growth of plants is, as a matter of course, the ground. Today, espctically in urban areas, spaces available for cultivating plants, e.g. lands, are quite limited, not to speak of sunny lands which are necessary for the growth of plants.
In light of the above-discussed situation, there has been proposed a system in which solar rays are converged by lenses or the like into a fiber optic cable so that the converged light may propagate through the cable to a plant cultivating apparatus, which may be located in any desired place. The light supplies optical energy to plants in the cultivating apparatus.
A solar collector heretofore proposed for use with such a system includes a number of lenses which are bundled up by a frame with a solar sensor mounted thereon. The lens assembly is rotatable about a first axis and a second axis which extends perpendicular to the first axis. The lens assembly and a drive mechanism associated therewith are encapsulated in a transparent dome-shaped housing. In operation, the lens assembly is moved about the first and second axes in response to an output of the solar sensor so that its light receiving surface is constantly directed sunward. The light converged by the lenses may be transmitted by a fiber optic cable to any desired place.
The problem with the prior art system described is that the light transmitted by the fiber optic cable contains direct solar rays but not indirect ones (skylight). In the growth of plants, skylight is necessary for the plants to maintain the base power for growth while direct solar rays (intense light) are necessary for the plants to germinate, flower and fruit and, further, for the fruits to grow and ripen. While plants perform photosynthetic reactions utilizing optical energy fed thereto and the resultant nutriment is transported to their trunks, fruits, etc., the transport occurs rather effectively when the plants are not illuminated, oxygen is present, and the temperature is relatively low. Stated another way, while photosynthetic reactions and the transport of nutriment produced thereby are essential for the effective growth of plants, it is preferable for effective photosynthesis that the supply of light to plants be interrupted repeatedly at predetermined intervals. No effective implementation has heretofore been proposed for the effective supply of combined direct and indirect solar rays for plant culture or for the intermittent illumination.